Download 3.1 How Changes Occur Naturally in Ecosystems

3.1 How Changes Occur Naturally in
Ecosystems

Natural selection - process where individuals
with advantages are better able to reproduce
and pass along their traits.
 A salmon with a smaller tail may never have a
chance to spawn because it can’t swim to the
correct location.

It is believed that all the
species are descended from
one finch species on the
mainland.

Each species has unique
characteristics that allows
them to thrive in their own
niche, and not compete with
other finches for the same
resources.
Adaptive radiation - a form of natural selection
when many different species appear from one
original species.
Example: The Finches of the Galapagos Islands
(off the coast of Ecuador)
There are 13 species of
finches on the island…
ECOLOGICAL
SUCCESSION
Changes in the biotic
characteristics in an
area over time.
Primary
Succession
Secondary
Succession
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Steps of Primary Succession
1. Starts with bare rock.
2. Wind carries spores of lichens that can survive
on bare rock.
3. Weathering breaks down rock
 soil begins to form
4. Pioneer species make soil
5. other plants can grow
Pioneer Species are the first organisms to
survive and reproduce.

Examples: Lichens and mosses
6. animals appear
7. a mature community forms
A Mature Community (also called a climax community)
is stable and only changes slowly over time
–
Ex. Old growth forests
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
Secondary Succession:
when an area already has soil, but has
had a disturbance like a forest fire or is
clearcut.
- it happens more
quickly than primary
because there is
already soil with
seeds, insects,
worms, etc.
There are many disturbances that
Might Cause Secondary Succession:
1. Flooding
– leads to soil erosion, spread of pollutants and
harmful bacteria associated with sewage
– climate change and global warming may be
increasing incidents
of flooding.
– could be caused by
a tsunami (when huge
waves, from large
earthquakes, flood
coastal areas.)
…in our forests there are a lot of old trees, the
climate is warming, and the bugs are not dying
in the winter.

Drought

Insect infestation
- Most insects are helpful, but when
normal conditions change,
infestations can occur.
- Example: Mountain Pine Beetle:
Usually it is not a problem…it helps
remove old trees, but….
- Pine beetle has blue stain fungus in its
mouthparts, which it transmits to the trees
(symbiotic relationship).
- Fungus slows down resin production on trees
so the beetle can eat the tree more easily.
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Modeling Succession Activity
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http://www.mrphome.net/mrp/succession.
swf
3.2 How Humans Influence Ecosystems
1. Land use: All of the land around us, even in cities,
was once a part of an ecosystem.
– We use the land for things like urban development,
agriculture, industry, mining and forestry.
Sumas Canal

The processing
and export of
resources like
lumber, coal and
sulphur are very
important to
BC’s current
economy.
2. Resource use: the ways we obtain and use
naturally occurring materials.
– Most products you use every day involve the use
of some natural resources in their production.
Human intrusion has caused many BC wetlands to
disappear.
– Wetlands are special ecosystems that contain
completely waterlogged soil for long periods of time.
– In the past 100 years up to 70% of the wetlands in
the lower Fraser Valley have been lost.
Why are they important?
- wetlands contain high
biodiversity, and filter
many impurities
out of the water.
- they can help prevent
flooding by storing water
after rainstorms
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3. Habitat Loss
- Because of human expansion, habitats have
been lost or fragmented.
“Habitat fragmentation” is the splitting of large habitats
into many smaller ones, resulting in disrupted natural
activities for plants and animals.
Habitat loss
Habitat fragmentation
4. Deforestation
Deforestation is the clearing or logging of
forests for human use.
– some land is never reclaimed or replanted.
– agricultural crops that are planted are often one
species = monoculture
 This reduces biodiversity, and leaves the crop
vulnerable to pests or disease.
 Polycultures, of many plant
species, are more economically
and biologically diverse.
– Deforestation results in soil degradation
(moving wind & water erode topsoil &
leave bare land behind).
 Topsoil: the upper layer of soil, is where most
of the nutrients, water and air are found for
plant growth.
– Deforestation is still occurring in
many tropical rainforests.
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5. Agriculture


In fields left without crops, water & wind can cause
erosion.
In wet areas the soil can become compacted.
– Soil particles are squeezed together
 This is due to farm animals or vehicles.
 There is no room for water or air to enter the soil.
6. Resource Exploitation:
= resource use
– Humans depend on resource
exploitation for jobs, materials,
food, shelter and energy.
– Exploitation can lead to habitat loss, soil
degradation & contamination of water supplies.
 Many mining and resource exploitations require
reclamation efforts.
– Reclamation attempts to reduce environmental
impacts of exploitation, and tries to restore the
original (or at least functional) habitats.
– Because of soil compaction water runs
off the soil instead of soaking in.
 causes leaching.
– Aeration, which involves removing
small plugs of soil, loosens
soil & can reduce run-off.
Overexploitation:
– the extraction of resources until they are
gone.
 Can result in extinction
– Example: passenger pigeon
 Food webs can be greatly affected for long
periods of time especially in keystone species
(species that greatly influence the population
numbers and health of an ecosystem)
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Sustainability of Ecosystems

Reducing Habitat Fragmentation
Definition #1: “The ability for an ecosystem to
maintain ecological processes”.
– ie. the ecosystem stays healthy naturally

Definition #2: “People using an ecosystem to meet
their needs today without reducing the function or
health of the ecosystem in the future”

Sustainable practices maintain,
or even improve, healthy ecosystems.
Returning young coho salmon
to rivers near Port Alice can
help maintain sustainability.
Traditional Ecological Knowledge:

In Aboriginal cultures it is passed down from
generation to generation.
– This knowledge reveals what past condition
were like, and also how the ecosystem and
humans interact.
– Knowledge is found in stories, songs, cultural
beliefs, rituals, community laws and traditional
practices.
– Current ecological restoration and usage
guidelines often involve this traditional
knowledge from Aboriginal representatives.
 Traditions such as the “Spring burn” allow for
ecological renewal.
 Fire suppression, enforced in BC for over 100 years,
has led to recent issues like the mountain pine
beetle infestation and huge wildfire losses.
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Invasive Species
3.3 How Introduced Species Affect Ecosystems
Native species naturally live in an area.
Introduced species (aka foreign species, non-native species,
exotic species or alien species).
– they have been introduced accidentally (& on purpose)
here over the past 400 years due to immigration.
– Many of these species are harmless, even beneficial.

Invasive species: are introduced species that often take
advantage of their new habitat.
– They may have no predators, are aggressive competitors,
& reproduce fast.
 Eg. Purple Loosestrife, negatively impacts native species, and
often reduces biodiversity as a result.
The sea lamprey arrived in the
Great Lakes via the canals and
St. Lawrence Seaway over 50
years ago, making its way
around Niagara Falls that at one
time protected the Great Lakes
from many east coast
species. They do millions of
dollars of damage to Great Lakes
fisheries each year.
The European
leaf-feeding
beetle (left), and
the Purple
Loosestrife.
The Impact of Introduced Species
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Competition: one species takes away resources from another.
Predation: if the invasive species is a predator, it may
have a huge advantage, as the native species may have no
methods to survive.
The Norway rat escaped from early European
explorer and fur-trading ships. On Queen Charlotte
Islands, they have caused a decline in groundnesting sea birds, such as ancient murrelets and
puffins, by eating their eggs and young.
50 breeding pairs of the European
Starling were brought to BC in the
late 1800’s. It now out-competes
western bluebirds for nesting habitat.
The American Bullfrog was brought
to BC in the 1930’s by restaurants
for their legs. It has since taken
over the habitats of native frogs.
West Nile virus was recently introduced to the United States
in 1999, when it started causing deaths in birds and illness
in humans in New York City. It is a vector borne disease,
carried by the mosquito.

Disease & Parasitism: by weakening certain species, a microorganism invading an ecosystem can drastically alter the
entire ecosystem and the niches within it.
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Habitat Alteration: some invasive species can change the
physical structure of the ecosystem by digging, burrowing,
blocking sunlight or changing the chemistry of the
ecosystem.
Eurasian Milfoil was first identified in
Okanagan Lake in 1970. It forms wide,
dense mats at lake surfaces, cutting off
sunlight to organisms below and
interfering with recreational activities. It
can grow from plant fragments, which
are often spread by boats.
 It
often takes human intervention to save
established ecosystems.
- The Garry Oak Ecosystem
Recovery Team (GOERT) is
trying to save several
ecosystems in BC because
Garry Oak trees are a keystone
species
- Scotch broom, English ivy
and other plant species are its
biggest threats.
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